Having a well managed Computer Network Diagram of your networking infrastructure where you are responsible with, is a must for documentation. It is not just for documentation purposes, you can use this LAN Network Diagram to make risk security assessment or create a critical assets register.
Unfortunately not all the network administrators develop their LAN network diagram particularly for small business or SOHO. But for medium-sized to enterprise class organizations, having a complete Computer network diagram is a must. Besides as documentation purposes, Computer network diagram can help you as the network administrators maintain and troubleshoot the networking problem and network management.
In the computer network diagram, all the networking devices should be identified by the IP address. If we are talking about the IP address, we should make a clear distinction in our LAN network diagram between the public IP address and the private IP address. The private address must be hidden from the public network (the Internet) by a NAT mechanism configured in the firewall. Typically a firewall is a barrier or a border line between the trusted-network (our private – internal network) and the un-trusted network (the internet). Therefore the firewall must be a secured system. See also guidelines in firewalls security and the IP address classes.
Generally computer network diagram can be shown in the following figure. The LAN network diagram can be divided by two different networks: the private network (which is behind the firewall) and the public network (the internet). The networking devices that sit in the public network typically consist of the CSU/DSU (which connect direct to the local loop of the Telco central office), a networking perimeter router (as the first line of defense against the internet threats), and the firewall. Typically in home usage, the manufacturers ship the three devices into a single all-in-one product particularly for broadband internet connection such as SURFboard SBG900 by Motorola. But many products ship with the function of the wireless router and the firewall separate from the modem such as WRT610N wireless router or Netgear wireless router.
Typical computer network diagram
In home usage, the wireless router typically has one WAN port (that connects direct to the LAN port of the modem with public IP address assignment) and 4 LAN ports with private address.
Redundant Computer Network Diagram
In medium-class or enterprise-class LAN network diagram, the computer network diagram is very complicated which might contain VLANs, redundant links, and sometimes contains multiple DMZs behind the firewalls. See also firewall topology.
The following is the example of the computer network diagram which contains redundant links for WAN connections, and also redundant links for each of the uplink switches.
Redundant LAN Network diagram
In the above computer network diagram, the uplink switches are supplied from different two core switches. All the switches must be STP enabled if you configure multiple switches redundantly to avoid broadcast storm. See also STP protocol for more detail about Spanning tree protocol.
If you also configure multiple VLANs, in your LAN network diagram should mark each of the computers with each VLAN IDs. The use of layer 3 Switching will improve the performance of the LAN network if the VLANs are implemented. See more detail VLAN tutorial about VLAN ID.
Computer network diagram will help you identify the critical items within the network, and you can make additional control for future disaster recovery. See also business continuity and disaster recovery plan and example of risk assessment.
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